The subject invention relates to methods for increasing the number of circulating CD4+ T-lymphocytes in HIV-infected patients by the administration of granulocyte-macrophage colony stimulating factor (GM-CSF).
Patients infected with Human Immunodeficiency Virus (HIV) experience a variable but progressive decline in immune function resulting in clinically apparent opportunistic infections and other diseases. (Crowe et al., J. Acquir. Immune Defic. Syndr. 4:770-76, 1991; Moss et al., AIDS 3:55-61, 1989). The onset of severe immunodeficiency in HIV-infected individuals is generally accompanied by a marked increase in viral load and a dramatic decline in circulating CD4+ T-lymphocytes. Indeed, one of the clinical criteria for the diagnosis and reporting of AIDS (as established by the Centers for Disease Control and Prevention) is a decrease in the number of CD4+ T-lymphocytes to  less than 200 cells/mL. (Normal CD4+ T-lymphocyte cell counts in healthy HIVxe2x88x92 individuals range between 800 and 1600 cells/mL.) CD4+ T-lymphocytes perform multiple immune-modulating functions. The decline in CD4+ T-lymphocytes, and decline in cell-mediated immunity, is the primary factor responsible for the susceptibility of HIV-infected patients to many opportunistic infections characteristic of the adult immunodeficiency syndrome, or AIDS. Accordingly, an increase in CD4+ T-lymphocytes is generally regarded as an indicator of efficacy for anti-HIV drugs.
Inhibition of HIV replication can increase CD4+ T-lymphocyte counts. Such antiretroviral therapy typically involves combinations of drugs such as protease inhibitors, nucleoside analogs, and non-nucleoside reverse transcriptase inhibitors. Other agents, including biologics, have also demonstrated some antiviral effects. The decrease in viral load is generally, but not always, associated with an increase in the number of circulating CD4+ T-cells. (Yarchoan et al., Ann Intern. Med. 115:184-89, 1991; Hirsch and D""Aquila, N. Engl. J. Med. 328:1686-95, 1993; Volberding, P. A., In: Crowe et al., eds., Management of the HIV-Infected Patient, pp. 53-63). Unfortunately, antiretroviral drugs do not result in complete reconstitution of the immune function. Moreover, inhibition of viral replication by these agents is temporary, due to the evolution of resistant strains of virus that can grow in the presence of the antiretroviral agents. (Cameroni et al., Third Human Retroviral Conference, January 1996, Abstract #LB6a).
Growth factor cytokines such as granulocyte-colony stimulating factor (G-CSF), granulocyte-macrophage colony stimulating factor (GM-CSF), and erythropoietin (EPO) have also been administered to patients with HIV. (Scadden et al., 1991, Levine et al., Blood 73:3148-54, 1991; Kaplan et al., J. Clin. Oncol. 9:929-40, 1991; Stricken and Goldberg, Clin. Immunol. Immunopathol. 79:194-96, 1996; Miles et al., Blood 77:2109-17, 1991; Pluda et al., Hematol. Oncol. Clin. North Am. 5:229-48, 1991). Recently, GM-CSF has been the subject of several studies to evaluate its ability to prevent opportunistic infections in individuals with HIV.
LEUKINE(copyright), a yeast-derived form of GM-CSF, is currently available for use in promoting myeloid cell recovery following bone marrow transplant post-myeloablative therapy for the treatment of malignancies. An E. coli-derived form of GM-CSF is also available for use in promoting the recovery of neutrophils in HIV-infected patients with granulocytopenia. (Scadden et al., J. Clin. Oncol. 9:802-08, 1991; Levine et al., Blood 78:3148-54, 1991; Kaplan et al., J. Clin. Oncol. 9:929-40, 1991; Hardy et al., Eur. J. Clin. Microbiol. Infect. Dis. 13:S34-S40, 1994). However, the widespread use of GM-CSF for treatment of HIV infection has been hindered by data from in vitro studies whose results suggest that this cytokine might actually enhance HIV replication (Bender et al., J. Immunol. 151:5416, 1993; Foli et al., Blood 8:2114, 1995; Pluda et al., Hematol. Oncol. Clin. North Am. 5:229-48, 1991). More recent studies have reported results which are inconsistent with earlier studies with regard to the effect of GM-CSF on HIV viral replication (Perno et al., Third Human Retroviral Conf., January 1996, Abstract #463; Pluda et al., Blood 76:463-72, 1990; Fletcher and Gasson, Blood 71:652-58, 1988; Mitsuyasu, R. T. In: Volberding and Jacobson, eds. AIDS Clinical Review, N.Y., N.Y. 1993-94, pp. 189-212). It is now believed that in the presence of antiretroviral therapy, GM-CSF does not upregulate HIV viral replication. (Scadden et al., 1995; Davison et al., J. Clin. Pathol. 47:855-57, 1994, Scadden et al., AIDS Res. and Human Retroviruses 12:1151-59, 1996). Indeed, in vitro data have demonstrated the enhancement of AZT activity by GM-CSF due to increased intracellular concentration of the active triphosphorylated form of AZT. (Hammer and Gillis, Antimicrob. Agents Chemother. 31:1046-50, 1987).
Developing effective therapies for HIV disease has presented a formidable challenge for medical researchers. Although significant advancements have been made in the treatment of HIV-infected patients, many patients remain untreatable due to ineffectiveness of the therapeutic drugs used or inability of the patients to tolerate the side effects of the therapies. Clearly, existing therapies do not yet offer a cure to HIV disease. Immune-modulating agents, such as GM-CSF, may therefore offer an additional alternative treatment.
The present invention provides methods for increasing CD4+ lymphocyte counts in HIV-infected patients by the therapeutic administration of GM-CSF. This method of treatment has been demonstrated to induce an increase in the absolute number of circulating CD4+ T-lymphocyte cells in patients concurrently receiving antiretroviral drugs, with no significant increase in viral load.
This invention is based on the results of a double-blinded, placebo-controlled study that enrolled HIV-infected patients at two study sites. In this study, patients receiving anti-retroviral agents for a minimum of eight weeks prior to study received therapeutically effective amounts of recombinant human GM-CSF or placebo. Viral load and CD4+ T-lymphocyte counts were determined twice prior to the start of the study (baseline), then two weeks, four weeks, and eight weeks after the start of the study, and twice approximately four weeks after the treatment phase was completed. Results indicated that within the placebo arm of the study, there was no significant change in the median values for CD4+ T-cell counts relative to the baseline. Within the GM-CSF arm of the study, a trend towards an increase in the median value for CD4+ T-lymphocyte counts was observed between the baseline and all evaluations during the course of the study.
The present invention provides methods for inducing an increase in the number of CD4+ T lymphocytes in an HIV-infected patient by administering therapeutically effective amounts of granulocyte-macrophage stimulating factor (GM-CSF).
In accordance with the present invention, GM-CSF is administered to HIV-infected patients in amounts and for a time sufficient to induce a clinically significant increase in the patient""s CD4+ T-lymphocyte count. A xe2x80x9cCD4+ T-lymphocyte countxe2x80x9d means the number of circulating CD4+ T-lymphocytes in the patient""s blood, expressed as CD4+ T-lymphocyte cells per unit volume. Generally, CD4+ lymphocyte counts are expressed as cells/mm3 of whole blood. An increase in the CD4+ T-lymphocyte count is defined as a rise relative to the baseline (i.e., before administration of GM-CSF) value. For the purposes of the present invention, a xe2x80x9cclinically significantxe2x80x9d increase in CD4+ T-lymphocyte cells is an increase of greater than or equal to about 30% of the baseline value.
GM-CSF used in the practice of the invention includes any pharmaceutically safe and effective human GM-CSF, or any derivative thereof having the biological activity of human GM-CSF. In a presently preferred embodiment, the GM-CSF used in the practice of the subject methods is recombinant human GM-CSF (rhu GM-CSF), such as LEUKINE(copyright) (Immunex Corporation, Seattle, Wash.). LEUKINE(copyright) is a biosynthetic, yeast-derived, recombinant human GM-CSF, consisting of a single 127 amino acid glycoprotein that differs from endogenous human GM-CSF by having a leucine instead of a proline at position 23. Other natural and synthetic GM-CSFs, and derivatives thereof having the biological activity of natural human GM-CSF, will of course be equally useful in the practice of the invention.
As the degree of glycosylation of biosynthetic GM-CSFs appears to influence half-life, distribution, and elimination, the most effective dose of GM-CSF for the subject methods may vary depending on the source used (Lieschke and Burgess, N. Engl. J. Med. 327:28-35, 1992; Dorr, R. T., Clin. Ther. 15:19-29, 1993; Horgaard et al., Eur. J. Hematol. 50:32-36, 1993). The optimal dose of GM-CSF used for LEUKINE(copyright) may be adjusted if a GM-CSF other than LEUKINE(copyright) is used to induce CD4+ T-lymphocyte cells in HIV-infected patients.
LEUKINE(copyright) has been shown to exhibit the same hematopoietic effects as those induced by endogenous GM-CSF, namely, the stimulation of progenitor cells committed along the granulocyte-macrophage pathway to form neutrophils, monocytes, macrophages, and eosinophils (Technical Product Report: LEUKINE(copyright) Liquid, Immunex Corp., Seattle, Wash., 1997, which is herein incorporated by reference). LEUKINE(copyright), like endogenous GM-CSF, also promotes the differentiation of progenitor cells giving rise to erythrocytes and megakaryocytes (Ibid.) In addition to stimulating hematopoiesis, LEUKINE(copyright) enhances many of the functional activities of mature neutrophils, monocytes and macrophages, such as chemotaxis, growth factor secretion, anti-tumor activity, antibacterial and antifungal activities, and so on (Ibid.).
Various embodiments of the subject invention are disclosed herein. In one preferred embodiment, GM-CSF may be administered concurrently with antiretroviral agents, including, but not limited to, nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, or protease inhibitors. The term xe2x80x9cantiretroviral agentxe2x80x9d, as used herein, includes any pharmacological, biological or cellular agent that has demonstrated the ability to inhibit HIV replication. Specific examples of nucleoside reverse transcriptase inhibitors include zidovudine (AZT), didanosine (ddI), lamivudine (3TC), stavudine (d4T), and dalcitabine (ddC). Specific examples of non-nucleoside reverse transcriptase inhibitors include nevirapine and delavirdine. Specific examples of protease inhibitors include indinavir, nelfinavir, ritonavir, and saquinavir. Patients treated in accordance with the present invention may be treated concurrently with one or more anti-retroviral agents. Additional antiretroviral agents not yet approved by the Food and Drug Administration may also be effective.
The optimal dose, frequency of administration, and duration of treatment with GM-CSF which is effective to induce a clinically significant increase in CD4+ T-lymphocyte counts may vary from patient to patient. Generally, however, therapeutically effective doses of GM-CSF sufficient to induce an increase in the patient""s CD4+ T-lymphocyte count will be greater than or equal to about 100 micrograms (mcg). Preferably, doses of GM-CSF will be greater than or equal to about 150 mcg, and more preferably, doses of GM-CSF will be greater than or equal to about 250 mcg.
In preferred embodiments of the present invention, GM-CSF is administered for a period of time greater than about three weeks, and more preferably greater than about four weeks, at a frequency of at least two times per week, more preferably at least three times per week, and most preferably once per day or more. However, it should be understood that the optimal dose and length of treatment may vary from patient to patient, depending on the individual patient""s condition and response to the treatment, and is best determined by monitoring the patient""s response during the course of the treatment. It should further be understood that administration of higher doses may permit less frequent administration, and lower doses may require more frequent administration in order to achieve clinically significant increases of CD4+ T-lymphocyte counts. A treatment regimen (dosage amount, frequency and duration) is therapeutically effective if it results in a clinically significant increase in CD4+ T-lymphocyte counts.
The methods of the subject invention thus include inducing an increase in the CD4+ T-cell count in an HIV-infected patient who may also be treated with an antiretroviral agent in which the patient is administered an amount of GM-CSF sufficient to induce an increase in the patient""s CD4+ T-lymphocyte count.